How do you weather a downturn in demand? His-and-hers brand icons Brooks Brothers and Maidenform are following a two-part formula to maintain market share and grow their customer base in down times: First, think timeless style, not hot-button fashion. And second, when you have the chance, hitch your wagon to a blazing star.

Maidenform is going from battle-axe to bombshell with a deal inking Mad Men stylist/design goddess Janie Bryant. She’ll be helping Maidenform boost sagging assets by spearheading a viral marketing campaign for the kind of vintage, form-flattering bras and slips that Maidenform has always specialized in.

One woman’s timeless classic is another’s hot flavor of the fashion season – and Maidenform, like Brooks Brothers, is savvy enough to know how to work both sides of that equation. Bryant will be repping such products as the Ultimate Push-Up Bra, Flexees control slip, and other “shapewear.” And what Maidenform does well, year in and year out, will get the brandlift it deserves.

Meanwhile, on the other side of the gender line, much the same process is playing out. As we’ve reported, Brooks Brothers has been making hay with the $998 branded Mad Men Edition suit. So much hay, in fact, that the men’s clothier is raiding Don draper’s closet one more time. Last week they announced their newly revamped homepage dedicated to neckties.

The knotty move may seem counter-intuitive given NPD’s findings that sales of neckties have plunged precipitously from $1 billion in the mid-1990s to just $418 million in 2009. Millennials have brought a new casualness to the workplace even as (largely because) wireless has dissolved the divide between home and office. And with the Men’s Dress Furnishing Association, a New York City-based trade group that shut down entirely in 2008, the traditional men’s clothing business has gone from fop to flop. Stir in one Great Recession, and you have a once-swaggering category dressed in rags and tatters.

But this is what makes Brooks Brothers – and Maidenform – so savvy. When you’re a premium leader, you don’t sway in the fashion breeze – their offerings are largely immutable. Yet when the merry-go-round of culture comes around to where you always are, grab the brass ring. For Brooks Brothers, the collapse of the competition, combined with a tasteful and timely co-branding opportunity with the Mad Men brand and their own undeniable standing as a standard bearer of timeless style, position them to consolidate market share and carry their category. With a portion of their site devoted to Mad Men Scenes and Janie Bryant’s Mad Men Portfolio, Brooks Brothers is looking Draper-suave.